Well head apparatus



Dec. 14, 1965 v. D. STONE WELL HEAD APPARATUS 2 Sheets-Sheet 1 FiledMarch 28, 1960 IN! L m IIH Hf I'M IIHHIH II I INVENTOR. V/QG/l 0. STONE47 7' ORNE Y! Dec. 14, 1965 v. D. STONE 3,223,168

WELL HEAD APPARATUS Filed March 28, 1960 2 Sheets-Sheet 2 56 i 45 62 a"f "/M M 4 6? 74 /0 2e 26 7a 50 /2 /2 /d INVENTOR. 4 P 5 V/QG/A a. 570M;

ATTORNEY United States Patent 3,223,168 WELL HEAD APPARATUS Virgil 1).Stone, Morgan City, La., assignor to Gulf Oil Corporation, Pittsburgh,Pa., a corporation of Pennsylvania Filed Mar. 28, B60, Ser. No. 17,847 1Claim. (Cl. 16689) This invention relates to the drilling of wells foroil or gas and more particularly to a well head assembly from which aplurality of string casings are suspended, and a method of drilling awell using the well head assembly in which blowout preventers connectedto the top of the well head assembly remain in place in operativecondition throughout the drilling for hanging of successive strings ofeasing.

During the drilling of oil and gas wells, it is usually necessary to setseveral concentric strings of easing before the well is drilled to itstotal depth. The usual procedure is to drill a hole to a depth slightlygreater than that at which a string of casing is to be set, set a stringof casing in the well, drill a hole of smaller diameter to a greaterdepth, set another string of casing, and repeat the process until thewell is drilled to the desired total depth. The apparatus and processesusually used in the drilling of wells required the removal of apparatususually referred to as blowout preventers after each string of easingwas set and connections at the well head made for subsequent drilling.The time required for disconnecting and reconnecting blowout preventersbetween each stage of drilling in some instances constitutes animportant part of the total time required for drilling and, hence, isresponsible for a substantial part of the cost of drilling a well.Moreover, the removal of blowout preventers from the well betweensuccessive stages of drilling leaves a well without any means forclosing it in if a surge of pressure should occur.

Danger from high pressure well fluids is particularly serious during thelatter stages of the drilling of a well when the depth of the well isgreatest. The larger size blowout preventers commercially availablegenerally are not capable of withstanding high pressures, hence theyoffer little protection during the latter stages of drilling. In thewell controls system conventionally used this caused no difiicultybecause of the practice of changing blowout preventers betweensuccessive drilling stages and the use of small blowout preventerscapable of withstanding high pressure during the drilling at the greaterdepths. However, when the drilling operation is performed through thesame blowout preventers from the time the conductor pipe is set, it isimperative that the blowout preventer be capable of withstandingpressures that may be encountered at any stage of the drilling. Thepractical eifect of this requirement is that a blowout preventer ofrelatively small size must be used during all stages of the drillingoperation.

It is important that the blowout preventers be in condition to functionproperly at all times during the drilling of the well. Proper operationof the blowout preventers can best be insured by providing means to testthem periodically during the drilling of the well. It is furtherimportant that leakage be avoided between one string of casing and thenext larger string of casing. To insure proper seals between successivestrings of casing, it is desirable that means be provided to allowtesting of the seals between an inner string of casing and the nextouter string of casing before the inner string is cemented in place.

This invention resides in a well head assembly in which a casing headtapered from its bottom to its top is secured to conductor pipe. Thecasing head has a landing surface of minimum diameter slightly largerthan the outer diameter of the largest inner string of casing to receivea boll 3,223,168 Patented Dec. 14, 1%65 weevil casing hanger from whicha string of casing is suspended within the well. A vent through thecasing head communicates with the central opening therein at a pointabove the landing surface to permit testing of blowout preventersconnected to the upper end of the casing head and seals betweensuccessive strings of casing. The drilling of the well is accomplishedin this invention by running a drill bit of substantially the same sizeas the largest inner string of casing through the blowout preventers andcasing head, and, either simultaneously with or after drilling the holefor the casing, underreaming the hole to the size necessary to allowcementing of the largest inner string of casing.

In the drawings:

FIGURE 1 is an elevation view, partially in section, of the well headassembly of this invention after completion of the drilling andsuspending casing and tubing within the well.

FIGURE 2 is a diagrammatic view showing, in elevation and partially invertical section, the well head assembly, before drilling for the firstinner string of easing, with a blowout preventer connected to the upperend of the casing head. The well head assembly is illustrated with thetest hanger used for testing the blowout preventer and the seals inplace.

FIGURE 3 is a diagrammatic elevation View, partially in verticalsection, illustrating the well head assembly as the first inner stringof casing is being run into the well.

FIGURE 4 is an elevation view, partially in vertical section, of thewell head illustrating the installation of a bowl protector in thecasing hanger for the first inner string of casing.

FIGURE 5 is an elevation view, partially in vertical section, of thewell head with the test hanger in place for testing the seals betweenthe casing hanger for the first inner string of casing and the landingsurface of the casing head and between the bowl protector and the casinghanger.

FIGURE 6 is an elevation view, partially in vertical section, of thecasing head with two inner strings of easing suspended from the landingsurface and with the test hanger in place for testing the seals.

In the following description of this invention, the first or largestinner string of casing is referred to for convenience as the protectorstring and the next string of casing is referred to as the oil string.Those terms have no particular significance to the invention. They aremerely terms used in the oil fields to identify inner strings of easing.

Referring to FIGURE 1 of the drawings, a casing head indicated generallyby reference numeral 10, is shown welded to the upper end of conductorpipe 12. The con ductor pipe 12 is set in accordance with the usualpractice and may be either driven in place or set in a previouslydrilled hole depending upon the conditions encountered at the particularwell site. The conductor pipe 12 is provided with a vent line 14equipped with a valve 15 for use in cementing the protector string ofcasing. The casing head 10 tapers from the bottom towards the top and isstudded at its upper end for connection with a blowout preventer 16, asshown in FIGURE 2 of the drawings, or upon completion of the well with atubing bonnet 18 as illustrated in FIGURE 1.

The casing head 10 has a central opening 20 extending vertically throughit. The walls of the central opening are substantially vertical butslope downwardly and inwardly slightly near the lower end of the casinghead to form a lower landing surface 22. A similar downwardly andinwardly sloping portion of the walls of the central opening 20 isprovided near the upper end of the casing head 10 to form an upperlanding surface 24. Landing surfaces 22 and 24 are substantiallyvertical but open upwardly to allow downward movement of casing andparent hangers onto the landing surfaces in the manner hereinafterdescribed. The diameter of the central opening 20 is larger at the upperlanding surface 24 than at the lower landing surface 22 to allow acasing hanger adapted to seat on the lower landing surface to passdownwardly into engagement with that landing surface.

It is desirable that the diameter of the central opening 20 be as smallas possible to reduce the total force of well fluids that might beexerted against the blowout preventer 16 to a minimum, and to reducethesize of the blowout preventer required. It is desirable that the maximumopening of the blowout preventer be slightly larger than the diameter ofthe protector string of casing to allow insertion of that casing and itsattendant hanger through the blowout preventer.

Suspended from a first casing hanger 26 seated in the landing surface 22is a string of protector casing 28. The casing hanger 26 is generallyreferred to as a boll weevil hanger which is run into the well integralwith the protector casing 28. As shown in FIGURE 1, a collar 30 connectsthe protector casing 28 and casing hanger 26 by means of threads 32. Thecasing hanger 26 is internally threaded at 34 near its upper end toreceive the threads of a landing nipple 72 (FIG. 3) on which theprotector casing 28 andhanger 26 are run into the well and landed ,onlanding surface 22. Casing hanger 26 has an upwardly facing inner bowlsurface 36 adapted to receive an oil casing hanger 38 from which astring of oil casing 40 is suspended. Hanger 38 like hanger 26 isinternally threaded near its upper end to receive a landing nipple onwhich the hanger 38 and oil string 40 are run into the well. Hanger 38is provided with an upwardly opening inner surface 42 against which atest hanger is adapted to seat to allow testing of the blowout preventerand seals between the two casing hangers in the manner hereinafterdescribed. Casing hangers 26 and 38 are provided with rings of packing27 and 39, respectively, in their outer surface for sealing against thelanding surface 22 and bowl 36.

An oil string vent 44 extends through the casing head and communicateswith the central opening 20 above the landing surface 22. Suitable pipeand valve means, not shown in the drawings, are connected to Vent 44 forcontrol of flow of fluids through the vent into or out of easing head10. A plurality of hold-down wedges 46 having sloping lower surfaces 48adapted to engage the upper surface of the hanger 38 are movableinwardly through the wall of the casing head 10 by suitable screwthreads to engage the upper end of the hanger 38. The hold-down wedgesserve to adjust the position of the hangers 26 and 38 against the lowerlanding surface 22 and the inner bowl 36, respectively and cause a tightseal between those two surfaces as well as to hold the hangers firmly inplace and prevent their movement in the event that they should besubjected to high pressures from the well.

Seated on the upper landing surface 24 in the casing head 10 is a parenthanger 50 adapted to receive tubing hangers such as 52 and 54. Theparent hanger 50 is held firmly in position by means of a plurality ofhold-down screws 56 extending through the walls of the casing head 10and engaging a groove 58 around the periphery of the parent hanger 50. Aslot 60 in the outer surface of the parent hanger 50 near its lower endreceives a parent hanger guide 62 to fix the angular position of theparent hanger 50 in the casing head 10. Tubing hangers 52 and 54 areprovided with rings of packing material near their upper and lower endswhich seal against the tubing bonnet 18 and parent hanger 50,respectively. In this manner, any pressure exerted by fluids withintubing strings 64, 65, and 66 suspended from tubing hangers 52 and 54and a third tubing hanger not shown in FIGURE l is transmitted to theChristmas tree assembly at the well head and is not applied against thecasing head 10.

The assembly of the apparatus illustrated in FIGURE 1 is accomplished inthe following manner. After welding the casing head 10 to the conductorpipe 12 and connection of the blowout preventer to the upper end of thecasing head, a test hanger 70 provided with a series of seating surfacesand rings of packing material on its outer surface is run into thecasing head 10 on drill pipe 71 and landed upon the lower landingsurface 22, as illustrated in FIGURE 2. Hydraulic pressure is thenapplied against the upper surface of the test hanger 70 through the oilstring vent 44 with the rams of the blowout preventer 16 closed againstthe drill pipe 71 and the blowout preventer and the well head assemblypressure tested. After completion of the pressure tests, the test hanger70 is withdrawn from the well. Test hanger 70 has an openingcommunicating with the bore of drill pipe 71 through which hydraulicpressure may be applied to test the springs of casing. A tail pipe 73may extend from the lower end of the test hanger.

Drill pipe from a bit attached to its lower end is then run through theblowout preventer 16 and the casing head 10. Circulation of drilling muddown through the drill pipe and drill bit up through the annulussurrounding the drill pipe is established in the conventional manner anddrilling of the hole within the conductor pipe is commenced. Thedrilling is continued to a depth slightly greater than the depth atwhich the protector casing is to be set. In order to provide space forthe sheath of cement around the protector casing the hole is underreamedwhile drilling to form a hole of larger diameter than the maximumopening through the blowout preventer 16 and easing head 10. The use ofan underreamer to enlarge the hole for the protector pipe allows use ofa blowout preventer of minimum size and capable of withstanding highpressures even though the hole necessary for the protector casing mustbe larger than the maximum opening of the blowout preventer andthecentral opening 20 of the casing head 10. For example, in a typicalinstallation using this invention, the conductor pipe 12 is 20 inches to30 inches in diameter and the protector casing is a 10% inch casing. Bymeans of this invention, a 12 inch blowout preventer having a maximumopening of 13 /8 inches, which allows collars on the casing and thecasing hanger 26 to pass through it, can be used. In this invention, thehole for the protector casing 28 is underreamed to 15 inches in diameterwhile drilling or prior to running the protector casing into the hole. Adrill bit which can be run through the twelve inch blowout preventer andthen expanded to make a fifteen inch hole also can be used.

The protector casing 28 connected to the lower end of the casing hanger26 is run into the hole on a landing mandrel 72, which may be a joint ofprotector casing, or as illustrated in FIGURE 3, a special nipple. Afterlanding the casing hanger 26 on the landing surface 22 of the casinghead 10 the landing mandrel 72 is unscrewed from the hanger 28 andremoved from the hole. A bowl protector 74, illustrated in FIGURE 4 ofthe drawings, is run into the hole on a bowl protector retriever 76 andseatd in the inner bowl 36 of the casing hanger 26. Bowl retriever 76 isprovided with lugs 78 on its outer surface adapted to slide throughgrooves in the lower inner surface of the bowl protector 74. Theretriever is rotated relative to the bowl protector after the lugs 78have passed through the grooves to move the lugs 78 out of alignmentwith the grooves and to a position for engagement with the bottomsurface of bowl protector 74. After the bowl protector is lowered intoposition the bowl protector retriever 76 is rotated to bring the lugs 78into alignment with the grooves and the bowl protector retriever iswithdrawn upwardly through the blowout preventer. Bowl protector 74 hasa machined inner surface adapted to receive and form a seal with one ofthe outer surfaces of test hanger 70.

The hold-down wedges 46 are then moved inwardly to engage the upper endof the bowl protector 74 and force it downwardly against the inner bowl36 of the casing hanger 26. The hold-down wedges 46 provide means forthe slight adjustment of the position of the bowl protector '74 to forma tight seal between the bowl protector and the casing hanger 26 andbetween the casing hanger 26 and the landing surface 22.

Referring to FIGURE 5, after the bowl protector has been placed inposition the test hanger 70 is run into the casing head and landed onthe inner surface of the bowl protector 74. The rams of the blowoutpreventer 16 are brought into contact with the drill pipe on which thetest hanger is supported. Liquid under pressure is then introduced intothe casing head 10 through the oil casing vent 44, and the blowoutpreventer and the seals between the casing hanger 26 and landing surface22 and between the bowl protector 74 and bowl 36 0f casing 26 aretested. If the test shows no leaks in the seals the protector casing 28is then cemented in place in the conventional manner by circulatingcement down through the protector casing 28 and up through the annulussurrounding the protector casing 28 and out through the surface pipevent 14. While waiting for the cement to harden a plug 80 in the hanger26 is removed by means of a suitable tool through an opening cut in theconductor pipe 12. A protector pipe vent 82 is then inserted through theopening in the conductor pipe 12 and screwed into the opening in thecasing hanger 26 from which the plug 80 was removed.

After the cement around the protector casing hardens, drilling isresumed and continued to the depth desired for the oil string of casing.Drilling mud is circulated down through the drill pipe and drill bit andup through the annulus between the drill pipe and the protector casingin the usual manner during the drilling. After completion of thedrilling, the bowl protector retriever is lowered through the blowoutpreventer into the casing head 10. The hold-down wedges 46 are moved outof engagement with the bowl protector and the bowl protector removedfrom its position in the bowl 36 of easing hanger 26. The oil string 40connected to casing hanger 38 is then run into the hole on a suitablelanding nipple connected to the casing hanger 38 by means of threads 84.After landing the casing hanger 38 in the bowl 36 of hanger 26 thelanding nipple is unscrewed and withdrawn from the well. The holddownwedges are then moved inwardly to engage the upper surface of casinghanger 38 in the manner illustrated in FIGURE 6 of the drawing. The testhanger 70 is run into the well to the position illustrated in FIGURE 6of the drawing to close the central opening of casing hanger 38 and theseals within the casing hanger and the blowout preventer are againtested. If the seals do not leak oil string 40 is then cemented inaccordance with conventional practice. Returns of liquid displaced fromthe hole during the cementing of oil string 40 are discharged throughprotector casing vent 82.

If it is desired to extend an open hole below the lower end of the oilstring 40 drilling can be resumed after the cement surrounding oilcasing 40 has hardened and the procedure described above repeated. Inthe apparatus illustrated in the drawings, no further drilling isperformed after setting the oil string 40. With the blowout preventer 16remaining in place on the upper end of the casing head 10, the parenthanger 50 is lowered into the upper landing seat 24 and held in thatposition by the hold-down screws 56. Tubing is then run into the wellthrough the parent hanger 50 in accordance with the conventionalpractice.

The apparatus herein described provides a simple well head assembly ofgreat strength and rigidity. The use of casing hangers of successivelysmaller outside dimensions for hanging successive strings of easingallows the opening at the upper end of the casing head to be onlyslightly larger than the largest inner string of casing. The opening ofthe oil casing vent into the casing head above the level of the landingsurface allows complete pressure testing of the seals between casingstrings before each of the inner strings of casing is set.

A divisional application, Serial No. 247,580, now Patent No. 3,190,354,describing and claiming the method of drilling a well described hereinwas filed on December 27, 1962.

I claim:

A wellhead structure comprising a unitary casing head having a boreextending downwardly therethrough, said bore comprising a lower portion,an intermediate portion, and an upper portion, said upper, intermediate,and lower portions having successively smaller diameters, an upwardlyopening upper landing surface between the upper and intermediateportions of the bore, an upwardly opening lower landing surface betweenthe intermediate and lower portions of the bore, a first casing hangerhaving casing secured thereto and extending downwardly therefromsuspended in the lower landing surface, said first casing hanger havingan upwardly opening interior seating surface, a second casing hangerhaving casing secured thereto and extending downwardly therefromsupported in said seating surface, said second casing hanger having anupwardly opening interior seating surface, wedging means extendinginwardly from the casing head and engaging the upper end of the secondcasing hanger and forcing said second casing hanger downward against thefirst casing hanger, a parent hanger suspended in the upper landingsurface, the upper end of the first and second casing hangers beingspaced below the lower end of the parent hanger, a port extendinglaterally through said casing head between the upper and lower landingsurfaces and opening into the intermediate portion of the bore above theupper end of the first casing hanger to provide communication with thecasing secured to the second casing hanger, a tubing hanger suspended insaid parent hanger and having tubing extending downwardly therefrom, anda tubing bonnet secured to the upper end of the casing head in sealingengagement with the upper end of said tubing hanger.

References Cited by the Examiner UNITED STATES PATENTS 1,189,516 7/1916Whitney 16646 1,849,374 3/ 1932 McEvoy 166-89 2,035,834 3/1936 Penick etal. 166-89 2,118,094 5/1938 McDonough et al. 16689 2,134,311 10/1938Minor et al 166-47 2,335,355 11/1943 Penick et al. 16686 2,478,6288/1949 Hansen 73-46 2,794,505 6/1957 Allen 16686 2,928,468 3/ 1960Wienands 16646 3,001,803 9/1961 Watts et al. 16675 X 3,177,942 4/1965Haeber 16666.5

FOREIGN PATENTS 855,369 11/ 1960 Great Britain.

CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDETT, BENJAMIN HERSH,

Examiners.

